These days, electronic apparatuses such as smartphones, tablet terminals, and notebook personal computers (PCs) are widely used, and functions and capabilities of these electronic apparatuses are improved day by day. With these advances, components such as processors and radio interfaces included in the electronic apparatuses generate more heat. However, it is not easy to improve the cooling capabilities of these electronic apparatuses due to their shape constraints. Thus, when a component is used in a high load condition for a long time, the component could not be cooled sufficiently. In this case, the heat could be transferred from the component to the surface of the housing of the electronic apparatus, and the surface temperature could increase.
One way to drop the surface temperature is to limit the operation level of the component when the surface temperature of the housing exceeds a threshold. For example, it is possible to drop the surface temperature by decreasing the operation speed of a processor or the communication speed of a radio interface. However, there are cases in which it is difficult to arrange a temperature sensor for directly measuring the surface temperature near the surface of the housing surface, due to the constraint on the shape of the housing. To solve this problem, the surface temperature may indirectly be estimated from measured data such as internal temperatures of the electronic apparatus.
For example, there has been proposed a housing surface temperature estimation method in which the surface temperature of a housing is estimated by using a temperature measured by a temperature sensor near a heat source and transfer functions. According to this proposed housing surface temperature estimation method, a transfer function representing the heat transfer from the heat source to the temperature sensor and a transfer function representing the heat transfer from the heat source to the surface of the housing are defined on the basis of a thermal circuit model including a thermal resistance and a thermal time constant. More specifically, by applying the two kinds of transfer function to the difference between the temperature measured by the temperature sensor and a reference temperature measured by a reference temperature sensor arranged far from the heat source, a surface temperature increase amount by the heat transfer from the heat source is estimated. Next, the surface temperature is calculated from the surface temperature increase amount and the reference temperature.
In addition, for example, there has been proposed a printer apparatus that estimates the ambient temperature of the housing by using a temperature sensor arranged in the housing storing a heat-generating component. The proposed printer apparatus assumes that the difference between a temperature measured by the temperature sensor and the ambient temperature falls within a certain range after a certain time elapses from power activation. Based on this assumption, the printer apparatus estimates the ambient temperature from the temperature measured by the temperature sensor and the elapsed time from power activation.
In addition, for example, there has been proposed a component temperature estimation apparatus that estimates the temperature of a component arranged a certain distance away from a heat source included in a vehicle. The proposed component temperature estimation apparatus calculates the temperature of the heat source and estimates the temperature of the component from the temperature of the heat source, the degree of the heat transfer from the heat source to the component, and the operating state of the component. In addition, for example, there has been proposed a data processing system that predicts change of the temperature of a processor from the ambient temperature, the current temperature of the processor, and the current operating state of the processor and changes the operating state of the processor on the basis of the predicted change of the processor temperature.
In addition, for example, there has been proposed a storage apparatus that controls a cooling fan on the basis of the ambient temperature. The proposed storage apparatus acquires a value of a first temperature sensor that measures the temperature of a heat-generating component and a value of a second temperature sensor that is arranged near the heat-generating component and that measures the outside air temperature of the storage apparatus. The storage apparatus calculates a correction value from the value of the first temperature sensor, the value of the second temperature sensor, and elapsed time and corrects the value of the second temperature sensor by using the correction value. See, for example, the following documents:
Japanese Laid-open Patent Publication No. 09-159541;
Japanese Laid-open Patent Publication No. 2010-276074;
Japanese Laid-open Patent Publication No. 2012-74064;
Japanese Laid-open Patent Publication No. 2015-10873; and
ISHII Masatoshi, NAKASHIMA Yoshiyasu, TAKAMOTO Kenshi, “Development of the Algorithm for Smartphone Surface Temperature Estimation with a Thermal Transfer Function Model”, Academic papers from the 30th Spring meeting of the Japan Institute of Electronics Packaging, pp. 212-215, Mar. 22, 2016
The above housing surface temperature estimation method assumes that the reference temperature measured by the reference temperature sensor is the same as or sufficiently close to the outside air temperature of the housing. However, due to the constrain on the shape of the housing, depending on the location of the reference temperature sensor, the reference temperature measured could be affected by the heat generated by the heat source. For example, since a heat source and a reference temperature sensor in a small electronic apparatus needs to be arranged close to each other, the reference temperature measured could be affected by the heat generated by the heat source. In this case, there is a problem that the estimation accuracy of the surface temperature is deteriorated.